Bend, Twist and Connect: The Rise of Flexible Connectors

The design and manufacture of connectors used in today’s electronic devices is experiencing a surge of innovation, instigated by the ongoing demand for ever smaller, more efficient and cleverer devices. One current trend worthy of our attention is the development and use of flexible connectors and stretchable connectors. These connectors sport the ability to bend, twist and stretch while continuing to function properly, making new applications in healthcare, wearables and flexible electronics possible. By leveraging these unique connectors in their own designs, engineers have an important building block here for developing groundbreaking next-generation products.

3 Key Technologies Behind Flexible and Stretchable Connectors

Flexible and stretchable connectors have been designed to maintain electrical connectivity even when undergoing deformation. They achieve this using advanced materials and innovative manufacturing techniques. Unlike traditional rigid connectors, which can break or lose functionality when they are bent or stretched, the connectors we’re talking about use flexible substrates and conductive materials to ensure the connector remains durable and functional in dynamically changing environmental conditions.

Conductive Ink: Conductive inks are important for those developing and manufacturing flexible and stretchable connectors. These interesting inks contain metal nanoparticles – such as silver or copper – which provide excellent conductivity, and these unusual inks can be printed onto different substrates. Advancements in the field are spurring the development of conductive inks created from sustainable materials. For example, this recent research published on nature.com shows the promise of biodegradable polylactic acid emulsion ink based on carbon nanotubes and silver being used for printed pressure sensors. This futuristic ink is biodegradable in marine environments, which minimizes the accumulation of toxic material in the ecosystem over time. 

Unique Flexible Substrates and Printing Techniques: Flexible substrates are a key ingredient for the creation of flexible or stretchable connectors. Base materials such as polyimide, silicone and thermoplastic polyurethane (TPU) provide the flexibility and durability that practitioners are looking for. The alchemy of the process all comes to fruition when advanced inkjet and 3D printing machines with an extremely high degree of precision deposit conductive inks onto one of these flexible substrates. 

For example, the company Nano Dimension, a leader in additive manufacturing, has developed innovative methods for printing multilayer flexible circuits. Their DragonFly IV is an additively manufactured electronics (AME) system capable of a unique process of precisely depositing conductive and dielectric materials, enabling the creation of complex, flexible connectors and other components.

Microfluidic Channels: Microfluidic channels are tiny fluid-filled pathways that have the ability to conduct electricity, offering a different approach to creating flexible or stretchable connectors. These channels can be integrated into flexible substrates to form highly adaptable circuits. In use cases where complexity and extreme agility are paramount – for example, with wearable health monitors – this technology is extremely valuable.

Applications for Flexible and Stretchable Connectors

Wearables: Flexible and stretchable connectors are changing the way wearables are designed as well as the functionality that can be provided by them. By enabling sensors to remain fully functional and provide accurate and reliable data – even when a user is being physically active – new product form factors and capabilities become possible. By utilizing these connectors, designers can create wearable products that deliver greater functionality combined with a delightfully comfortable fit. 

According to Grand View Research, the global wearable technology market was $61.3 billion in 2022 and is forecast to grow with a compound annual growth rate (CAGR) of 14.6% from 2023 to 2030. With the potential for breakthrough advancements to come, this may be an overly conservative forecast.

Healthcare and Medical Devices: In healthcare, flexible connectors are a critical enabler in the ongoing development of advanced medical devices that are less invasive and more comfortable for patients. For example, stretchable ECG monitors can be worn on the skin to continuously monitor heart activity without the discomfort many patients experience when using traditional rigid electrodes. For an extensive examination of the topic, see Flexible Electronics and Healthcare Applications in the journal Frontiers in Nanotechnology.

Flexible Electronics and Displays: Flexible connectors allow for the integration of electronic components into flexible screens, thus enabling fascinating new form factors for a range of devices including smartphones, tablets, laptops, televisions and wearable displays. Industry behemoths Samsung and LG are at the forefront of this sexy technology, developing flexible OLED screens that can be folded or rolled without damaging the internal circuitry.

Soft Robotics:  Soft robotics is an emerging field that’s about building robotic components created with materials that are highly compliant, often trying to replicate the flexibility and physical characteristics and capabilities of humans or animals. Flexible and stretchable connectors are critical enablers for those developing new soft robotics systems. They allow the integration of electronic components, sensors and actuators into the deformable structures of soft robots, without compromising a robot's flexibility or functionality.

Challenges Facing Adoption

Durability and Reliability: One of the biggest challenges in the development of flexible and stretchable connectors is making sure that they are durable and reliable with repeated use and even ‘abuse.’ To address this challenge, manufacturers are continuing to explore a world of new possible materials and a number of sophisticated protective coatings that will enable the next generation of flexible and stretchable connectors to work reliably despite repeated mechanical stress. In addition, the development of advanced fabrication methods – such as selective laser sintering and annealing – are ongoing, aiming to improve the adhesion and conductivity of printed circuits, with the overarching goal of enhancing durability.

Manufacturing and Scalability: Scaling the production of flexible and stretchable connectors to meet the potential demand has been a significant challenge for some time, and this challenge persists today. The precise manufacturing processes required, stubbornly, continue to be both costly and time-consuming. Nonetheless, some potentially meaningful advancements in printing technologies and materials science are helping to make their mark on improving development and manufacturing processes. For instance, roll-to-roll printing techniques that were developed for the production of flexible solar panels are being adapted to make the production of flexible electronic components more efficient.

The outlook for flexible and stretchable connectors is promising. Ongoing advancements are expected to drive further breakthroughs. Emerging applications in fields ranging from smart textiles to biocompatible devices and advanced robotics will likely benefit immensely. 

Hidden Heroes of the Digital World: Sometimes the most basic components wield great power. As a professional designer or engineer, you can access this power by taking advantage of the innovations in connector technology discussed here as tools for bridging gaps, shrinking distances and enabling seamless communication in your designs.